This invention relates to piston seals, and specifically to a piston having a seal formed thereon. The piston and seal of the invention are particularly suited for use as a floating piston with seal.
A floating piston is used to separate a gas from a liquid in a hydraulic cylinder. The floating piston moves axially when a pressure drop across it is sufficient to overcome seal friction. There is no actuation rod attached to a floating piston. Conventional pistons are enclosed in a cylinder and connected to an actuation rod.
Floating pistons are commonly used in hydraulic accumulators and gas-loaded shock absorbers. Shock absorbers used for car and truck suspensions, and shocks for bicycles, snowmobiles and truck seats use millions of floating pistons. Prior art floating pistons and conventional pistons use a screw-machined aluminum or steel plug, having an O-ring, or similar seal, groove or surface irregularity machined into the outer surface of the plug, and an elastomer seal received in the groove or on the irregularity.
U.S. Pat. No. 3,388,638, to Brinkel for Piston, granted Jun. 18, 1968, describes a piston wherein the piston body and seal are fabricated as an integral unit, which appears to be manufactured from an elastomer material. As such, there is no distinction between the piston and the seal.
U.S. Pat. No. 3,703,125, to Pauliukonis for Plastic actuating cylinder, granted Nov. 21, 1972, describes a piston and a cylinder having an integrally molded end closure. The piston and cylinder are formed of plastomer material. The piston and seal appear to be formed from the same material (FIG. 4).
U.S. Pat. No. 4,214,507, to Hock et al. for One-piece plastic piston, describes a piston having a rigid thermoplastic molded core and a seal element molded in the core from a flexible thermo plastic material thereby forming a unitary assembly. The piston has a flange formed about its periphery to retain a seal thereon.
U.S. Pat. No. 4,821,627, to Leigh-Monstevens for Piston and cylinder assembly, granted Apr. 18, 1989, describes a piston and cylinder assembly wherein a seal may be secured to piston by dipping and end portion of the piston into an adhesive, placing the end portion into a molding tool, closing the tool, and injecting rubber into the tool in a surrounding relation with respect to end portion 20b, resulting in a bonding of the rubber material to the piston. The piston configurations incorporate some irregularity, to secure the seal to the piston.
U.S. Pat. No. 5,070,971, to Dourson et al. for Molded piston for a hydraulic damper, granted Dec. 10, 1991, describes a molded piston which is formed of a flexible plastic.
A method of forming a piston includes fabricating a piston cup, wherein the piston cup includes a top, a sidewall void of any seal-gripping irregularities, and an open end, and forming an elastomer seal over the sidewall, and, in some instances, over the top, of the piston cup.
A piston includes a piston cup having a top, a sidewall extending about the periphery of the top and an open end, wherein the sidewall is void of any seal-gripping irregularities. An elastomer seal is formed about the sidewall of the piston cup.
It is an object of the invention to provide an integrally formed piston and seal therefor.
It is another object of the invention to provide a floating piston which is easy to manufacture, and which has a relatively low manufacturing cost.
This summary and objectives of the invention are provided to enable quick comprehension of the nature of the invention. A more thorough understanding of the invention may be obtained by reference to the following detailed description of the preferred embodiment of the invention in connection with the drawings.